Under cold start conditions, a powertrain has cooled to ambient conditions, which may be relatively hot or cold, and each component of the powertrain (e.g., engine, transmission, etc.) warms-up to a desired operating temperature. It is desirable for the powertrain to warm-up as quickly as possible, as the powertrain operates with increased fuel economy when it is up to operating temperature. Further, it has been shown that, of the various powertrain fluids (e.g., engine coolant, transmission fluid, engine oil, etc.) heating transmission fluid returns the largest fuel economy benefit.
In some examples, the transmission fluid is heated via heat exchange with engine coolant which is circulated through a cylinder block and cylinder head of the engine. In such an example, the transmission fluid is heated after the engine coolant is heated. In other examples, the transmission fluid may exchange heat with air, including via a radiator, and the transmission fluid may only be heated if the radiator is running hot.
The inventors herein have recognized the above issue and have devised an approach to at least partially address it. Thus, a method for lubricating a transmission with transmission fluid, the transmission coupled to an engine in a vehicle is disclosed. The method comprises directing the transmission fluid through a cylinder block adjacent to a cylinder wall, and, under a first condition, directing the transmission fluid to a heat exchanger and, under a second condition, bypassing the heat exchanger.
Thus, by directing the transmission fluid to flow through the cylinder block adjacent to the cylinder walls, the transmission fluid may be heated as soon as engine waste heat is generated thereby increasing fuel economy during a cold start, for example. In addition, engine coolant may flow through the cylinder head while transmission fluid flows through the cylinder walls and the cylinder block may remain at a higher temperature than the cylinder head, while reducing requirements to transfer fluid between the head and the block. Further, by controlling the flow of the transmission fluid to a heat exchanger, the temperature of the transmission fluid may be regulated such that it does not get too hot.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.